This invention relates to novel crosslinking agents for use in finishing baths for textiles and to a process for finishing textiles to render the textiles wrinkle resistant and/or iron free.
Cellulosic fabrics or textile materials are presently generally rendered wrinkle resistant or iron free in a process known as the cotton durable press process (DP process). In such a DP process, cellulosic fabrics are treated in a finishing bath with one or more finishing agents, generally to crosslink the cellulose molecules. Such crosslinking of the cellulose imparts to the fabric a tendency to return to its original shape and smoothness.
Formaldehyde, formaldehyde derivatives and formaldehyde addition products with urea, carbamate esters and other amidic compounds have been extensively used in the past as the crosslinking agents in such a process. However, serious drawbacks or problems have been found to exist with the use of such formaldehyde-derived crosslinking agents, particularly due to the release of dangerous and toxic formaldehyde vapors during the DP process and during subsequent manufacture, use, sale, laundry, and storage of garments made from such crosslinked fabric. In fact, regulations in various countries limit the dose of exposure of formaldehyde to which one can be exposed to a very low dosage amount, and for the most part effectively limit or prevent the use of such formaldehyde derivatives in the process.
In an attempt to avoid the use of formaldehyde or formaldehyde-derived crosslinking agents, several other crosslinking agents have been suggested. For example, in PCT Application No. PCT/US89102628 (WO 89/12714) of the US Department of Agriculture, there is a proposal to use organic polycarboxylic acids as crosslinking agents with hypophosphite, phosphite or polyphosphate curing catalysts to render cellulosic textile materials wrinkle free. Also, U.S. Pat. No. 5,300,240 and EP 0 976 867 A1 disclose that phosphinicosuccinic acid, phosphinicobissuccinic acid, or mixtures thereof can be used as crosslinking agents for cellulosic textile materials to render them wrinkle resistant.
However, there is still a need for other cellulosic crosslinking agents for rendering cellulosic textile materials wrinkle resistant that do not release formaldehyde vapors and yet provide wrinkle resistance to the cellulosic material that is as good as that provided by formaldehyde-derived crosslinking agents. Further, there is a need for other non-formaldehyde derived crosslinking agents that function better as cellulosic crosslinking agents than replacement crosslinking agents heretofore proposed.
It has been discovered that certain phosphinato-substituted polycarboxylic acids, and suitable salts thereof, function as superior crosslinking agents for cellulosic textile materials or fabrics. The phosphinato-substituted polycarboxylic acid cellulosic crosslinking agents of this invention are phosphinato-substituted propanetricarboxylic acids, phosphinato-substituted butanetetracarboxylic acids, oligomers thereof and mixtures thereof. Also, mixtures of the foregoing with phosphonato-substituted derivatives of these polycarboxylic acids can also be employed as crosslinking agents in a DP process for rendering cellulosic materials wrinkle resistant and iron free.
The phosphinato-substituted alkanepolycarboxylic acids and salts thereof useful for crosslinking cellulosic materials, especially in a DP process, comprise compounds of the formula (I) and obligomers thereof 
wherein R is H or 
preferably 
R1 and R11 are each independently H, C1 to C4 alkyl or xe2x80x94CH2COOM in which M is H, Na, K or NH4, preferably R1 and R11 are H or xe2x80x94CH2COOM in which M is H or Na;
R2, R3, R4, R8, R9 R10 are independently H or C1 C4 alkyl, preferably H;
R5, R6, R7, R12, R13 and R14 are each COOM1 in which M1 H, Na, K, or NH4, preferably xe2x80x94H or xe2x80x94Na; and
A is OH, H, C1 C8 alkyl, cyclohexyl, aryl or OM2 in which M2 is H, Na, K or NH4, and A is preferably OH or ONa.
A preferred class of compounds are phosphinatobis(propane-1,2,3-tricarboxylic acid) and the sodium salt thereof of formula (II) and oligomers thereof and phosphinatopropane-1,2,3-tricarboxylic acid and the sodium salt thereof of formula (III) and oligomers thereof 
wherein A1 and A2 are each independently OH or ONa.
Among the oligomers of the compounds of formula (I) there may be mentioned oligomers of formula (IV) 
wherein R2, R3, R4, R5, R6, R7, R8, R9, R10, R12, R13, R14 and as defined for formula (I) and m and n are each independently a small whole numeral and m plus n is greater than 2. A preferred group of oligomers are oligomers of formula (IV) in which R2, R3, R4, R8, R9 and R10 are each H; R5, R6, R7, R12, R13 and R14 are each COOM1 where M1 H resulting in an oligomer of formula (V) 
where m and n are as defined for formula (IV) and A3 is OH or ONa.
Another group of oligomers of the compounds of formula (I) are oligomers of formula (VI) 
wherein A4 is OH or ONa and m1 is a small whole number equal to or greater than 2.
Another crosslinking agent within the scope of formula (I) is wherein R is 
and R5, R6, R7, R12, R13 and R14 are each COOM1 where M1 is H; R1 and R11 are each xe2x80x94CH2COOM wherein M is H; R2, R3, R4, R8, R9 and R10 are each H and A is OH, namely phosphinatobis(butane-1,2,3,4-tetracarboxylic acid) or the sodium salt thereof of formula (VII), 
where A5 is OH or ONa.
A still further class of crosslinking agents within the scope of formula (I) are C1-C8 alkyl, cyclohexyl or arylbis(polycarboxyalkyl)phosphine oxides, such as butylbis(1,2,3-tricarboxypropyl)phosphine oxide of formula (VIII), 
Compounds of formula (I) can be prepared by any suitable process, such as for example, by reacting an unsaturated acid such as prop-1-ene-1,2,3-tricarboxylic acid or but-1-ene-1,2,3,4-tetracarboxylic acid or derivatives thereof with hypophosphorous acid or an alkali metal or ammonium hypophosphite or an alkyl-, cyclohexyl-, or arylphosphine, or phosphine oxide under recognized appropriate conditions of stoichiometry, pH, temperature and free radical initiators. As examples of suitable free radical initiator, there may be mentioned persulfates such as sodium or ammonium persulfates, t-butyl hydroperoxide and other similar free radical initiators.
A process for finishing cellulosic materials, such as textiles or fabrics, is provided by employing one or more of the compounds of formula (I) and oligomers thereof and a curing catalyst in a finishing bath to treat the cellulosic material so that the cellulosic material is impregnated with the crosslinking agents of this invention. In general, the finishing bath will be a solvent solution, preferably an aqueous solution, containing a wrinkle free-providing effective amount of a crosslinking agent of this invention and a curing catalyst. Generally, the finishing bath will contain from about 2 to about 20%, preferably from about 5 to about 15% by weight of crosslinking agents, and from about 0.5 to about 10%, preferably from about 3 to about 8% by weight of curing catalyst. The finishing solution may have other suitable ingredients or agents present, such as for example, a fabric softener, solvents, wetting agents, buffers or the like. The pH of the finishing bath will generally be about pH 2 to pH 4.
In general, the cellulosic material is impregnated with the crosslinking agent and curing catalyst by immersing the cellulosic material in the finishing bath. After the cellulosic material is thoroughly wet in the finishing bath, the cellulosic material is passed between squeeze rolls to remove excess liquid. The cellulosic material is then preferably dried followed by curing in a suitable oven at a temperature of generally from about 150 to 250xc2x0 C. for a period of generally up to about 15 minutes, preferably about 1 to 5 minutes, to cause crosslinking of the cellulosic material to occur. If desired, the crosslinked cellulosic material may be subsequently given a rinse to remove unreacted crosslinking agent and curing catalyst, and then redried.
The crosslinking agents of this invention can be employed to finish any suitable cellulosic material, generally any material containing about 25% or more cellulosic fibers, such as cotton, flax, jute, hemp, ramie, and regenerated unsubstituted wood cellulosic, such as rayon. The cellulosic material can be, for example, in the form of woven and nonwoven textiles, such as yarns, knit fabrics, or fibers, linters, rovings, slivers and the like.
The invention is illustrated, but not limited, by the following examples.
Preparation of crosslinking agents of this invention is illustrated by Examples 1 and 2.